Try relocating the speakers, making sure that the speaker wires aren't next to any power cords. I've seen this happen more than once, where the power cords interfere with the sound coming out of the speakers. I've also seen a friends computer speakers pick up his cordless phone
You can try adjusting the settings in the audio properties and making it 4 speakers (probably 4.1) to see if that'll make a difference. It may or may not, as there's nothing to seperate the sound to each individual speakers, as there's still only 2 lines going to 4 speakers so the computer recognizes 2 speakers. In a 4.1 or higher surround sound, the signal is broken up at either the sound card (or onboard audio) or at the subwoofer which delivers the "surround sound".
You never know, it might work! Give it a whirl! Good luck with it, I hope it works for you!
War produces veterans, wounded both physically and mentally. They have sacrificed for us.....and it is now our job to help these veterans, as they have already helped us in ways we will never know, in ways that we cannot fathom, and in ways that we take granted every day.